Why the shrimp head turns black: In fact, the blackening of the shrimp head has nothing to do with heavy metal pollution or freshness. In fact, it is caused by the shrimp itself, which has a great relationship with the diet and growth of the shrimp. It belongs to an enzymatic browning reaction in shrimp. In addition, algae eaten by shrimp or feed eaten by artificially fed shrimp can also lead to the blackening of shrimp head. This is a natural change of shrimp head, which does not mean that shrimp is polluted by heavy metals, even if shrimp is polluted by heavy metals.

It will not be so obvious on the shrimp head. It is difficult for the naked eye to tell whether there are heavy metals, and further tests are needed. However, shrimp head is really not recommended to eat, and it is the place where heavy metals gather in prawns. In addition, if the shrimp is refrigerated or frozen, it will indeed cause the head of the prawn to turn black, but it cannot be said whether the shrimp is fresh or not.

When buying prawns, how to judge whether the prawns are fresh or not? Pay special attention to the freshness of food when buying meat, and the same is true for prawns. Everyone wants to buy fresh prawns to eat. Not only to be harmless to the body, but also to taste better.

How to judge the freshness of shrimp meat is a technical activity. When buying shrimp, we should pay attention to the following points: whether the shrimp head is separated from the shrimp body, if it is, it is not fresh; Whether the shrimp shell and the shrimp meat are separated is not fresh; Whether shrimp meat is elastic or not, it is stale without elasticity; If the shrimp shell is red, it is stale (excluding cooked shrimp), and if it has a rotten smell, it is stale.

In addition, when eating out, you should be especially careful. Many prawns mixed in seafood stalls are stale, and the prawns with particularly cheap prices are basically stale leftovers. The shrimps cooked with heavy tastes may also be stale, which is conducive to covering up the bad smell!

If the shrimp you buy has no "blackheads", but it will not turn black after being cooked for a while, then it means that you are not cooked thoroughly, so you should eat it carefully.

Finally, I would like to remind you that when eating seafood such as shrimp and crabs, you must cook them thoroughly to avoid other symptoms such as diarrhea caused by parasitic infection or bacterial infection. People who are allergic to seafood are not recommended to eat shrimp to avoid allergic symptoms.